Method and apparatus for the production of music



June 27, 1933. B. F. MIESSNER 1,915,358

METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC 'Original Filed April9, 1951 3 Shets-Sheet l INVENTOIQ,

- June 27, 1933. B. F. MIESSNER METHOD AND APPARATUS FOR THE PRODUCTIONOF MUSIC Original Filed April 9. 1931. 3 Sheets-Sheet 2 AFIF. L.5.

ys l u f I J INVENTOR,

A ORNEY.

June 27, 1933. B. F. MIESSNER 1,915,853

METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed April 9,1931 3 Sheets-Sheet 3 Am? L5.

INVENTOI;

ATTNEY.

Patented June 27, 1933 UNITED STATES PATENT OFFICE ASBIGNOB TO KIESSKEBINVENTIONS,

METHOD AND APPARATUS FOR THE PBODUCTIOK OI MUSIC Application fled April8,

This invention relates to musical instruments and systems in which tunedvibrating bodies are used, their vibrations translated into electricoscillations, and such osclllations employed for the actuation offurther apparatus and more specifically to mechamcoelectric translatingdevices and their employment in such instruments and systems fortranslating the vibrations of the tuned bodies into electricoscillations. In my coending application, filed January 30, 1931, erialNumber 512,399, I have methods and apparatus of this nature, 1ncludingseveral forms and uses of such translating devices. This application isin part a continuation of the above-mentioned, dealing with improvementsin the electromagnetic translating devices and methods ofemploymenttherein described, as well as Wlth alternative forms of translatingdevice.

'Although the methods and apparatus hereinafter disclosed are suitablefor use with any form of tuned vibrating body, they are especiallyadaptable to use with strings. While the invention contemplates bodiesexcited into vibration in any consideration has been given to bodiesexcited by percussion, which excitation in instruments of the classdescribed often entails certain peculiar problems. Prominent among theseproblems is that of the reduction of an undesirable rap or thudsuperimposed upon and occurring at the commencement of the tonesproduced by the individual bodies, particularly those tuned to highervibration frequencies. Thus my invention has as a specific object thereduction or elimination of.

this rap and of other undesirable effects particularly likely to beencountered in the case of percussion excitation. A further specificobject of my invention, equally important with any form of excitation;is the elimination of introduction of undesirable harmonies by thetranslating device in the oscillations therein generated.

A general object of my invention is the provision of improved devicesand manner of employment thereof for translating the vibrations of tunedbodies into electric oscillations; and a further object is the provisiondisclosed certain manner, special 1931, Serial No. 528,750. RenewedAugust 5', 1932.

of improved means and methods, involving such translating devices, foradjusting the relative volume of the different tones, andfor varying thevolume of all the tones, produced in the output of an instrument orsystem of the class described. Other and allied objects will more fullyappear from the following description and the appended claims.

In the detailed description of my invention hereinafter set forth,reference is had to the accompanying drawings, of which Flgure l is a.perspective view of a single vibratory string provided with translatingdevices designed for the reduction of the rap effect abovementioned; ras Figure 2 is a cross-sectional view of a group of strings providedwith translating devices designed for the same purpose and for theelimination of spurious harmonic generation;

Figure 3 is a side view and Figure 4: a cross-sectionalyiew of a stringprovided with translating devices designed for such spurious harmonicelimination and for the suppression a of periodic oscillation amplitudevariation;

Figure 5 is a side view of a pluralitv of strings provided withtranslating'devices and means for manipulating the same for the controlof the individual amplitude and the general amplitude of the electricoscillations generated therein;

Figure 6 is a plan view of a portion of an electrical musical instrumentillustrating an alternative arrangement of translating devices;

Figure 7 is a plan view and Figure 8 a cross-sectional view of a portionof an electrical musical instrument employing a modified form oftranslating device; and

Figure 9 is a perspective view of a portion of a musical instrumentemploying a further modified form of translating device.

I have above referred to the phenomenon of rap frequently attendant uponthe commencement of the tone produced by percus sion excitation,particularly of strings, in an electrical musical instrument of theclass described. In Figure 1 I show an arrangement of translating devicewith which this 1M disturbance may be minimized. In this figure, 1 isasection of a string of magnetic material, such as the usual steel musicstring, which may be caused to vibrate by hammer 2, striking it frombeneath. The translating device 11 is seen to consist of a bar magnet 21having afn'xed thereto pole piece 3 separated from string 1 by gap '6,and carrying near such pole piece coil 31. The output terminals of coil31, across which appears the output of the translating device, may beconnected to the in ut terminals of an electrical amplifier 4, in t eoutput circuit of which I show loudspeaker or other electro-acoustictranslating device 5. An explanationof the reduction of rap by atranslating device of this design is as follows The magnet 21, the polepiece 3, the gap 6, the portion of the string near the pole piece, andthe air path from such portion back to the lower end of magnet 21 ingeneral form a magnetic circuit threading coil 31; and variations in thereluctance of this circuit, produced by variations of the gap 6, cause avoltage to .be induced in coil 31, as. will be understood. If the stringbe suddenly and appreciably moved directly toward or away from polepiece 3, a large transient voltage is set up in coil 31 and, amplifiedby 4 and translated into sound by 5, appears as the rap of which mentionhas been made. In Figure 1, however, it will be seen that the sudden andrelatively large motion of string lwhich is the result of impact ofhammer 2 is neither directly toward nor away from the pole piece, beingparallel to its face. Th s the magnitude of the transient voltage isgreatly reduced.

Should the string be caused by such impact to vibrate purely in avertical direction, it is true that there would result poor efficiencyof translation of its vibration into electric oscillation, and that suchtranslation as occurred would be principally bicyclic. I havediscovered, however, that in almost no case is it possible so to strikea string as to preclude the excitation of an appreciable component ofvibration in a plane at right angles to the direction of striking-4. e.,in a horizontal plane as shown in Figure 1and that as a result theimpairment of eflicie'ncy of action of the translating device is by nomeans as great as the reduction of the rap.

Various modifications of the design of this translating device may bemade wthout impairing its eflicacy in reducing rap. Thus, with referenceto Figure 1, the magnet 21, carrying coil31, may be mounted horizontallywith its pole in the position in which the pole piece 3 is shown, thelatter being omitted. Or, again, the ole piece may be omitted and themagnet ra sed slightly with respect to the string, so that its pole liesalongslde and near to, but not pointed at, the string. This lattermodification is illustrated by the translating device 10 drawn inFigure 1. Some reduction in translating efficiency occurs withtranslating device 10, due to the ositioning of the string in a lessintense held; but the simplicity of the arrangement, particularly in aninstrument employing a lurality of strings, has much to recomlnen it.

In Figure 2 I show a plurality of strings 1, which may if desired beparallel and in a single plane, and a plurality of the translatingdevices 12, com and coils 32 prefera ly connected in series. A singlehammer 2 is shown, denoting a vertical striking direction; it will ofcourse be understood that a hammer may be employed for each string ifdesired. In this arrangement the vibrations of each string 1 aretranslated by two of the devices 12, i. e., those on either side ofthe'string. It is therefore important so to phase the coils and pole themagnets that the voltages induced by the vibration of each strin in thetwo adjacent coils aid, and do not buc each other; and the arrangementwhich I prefer for the accomplishment of this objective comprisessimilar poling of the magnets 22-i. e., the mounting of all with likepoles upsim1lar placement of similarly wound coils 32 thereon, andconnection of the bottom of the first coil to the bottom of the second,of the top of the second to the top of the third etc. as shown. Reversalof the polarity of any magnet however, if accompanied by the reversal ofrising bar magnets 22 the phase of its coil, will still not causebucking induced voltages.

The large vertical component of the motion of any of the strings is inthis case translated with even less eflicienoy than in that of thestring shown in Figure 1, and is theoretically not translated at all ifthe two translating devices adjacent the string are symmetrical aboutit. This results from the arrangement of polarities and phases, whichcauses voltages induced by vertical vibration components to buck oroppose each other. Horizontal vibration components are present asbefore, however; and to these the arrangement shown is particularlyresponsive, a motion of the string toward one translating device andaway from the other inducing voltages in the coils of the two deviceswhich add. Modifications of translating devices in this arrangement maybe made, one being illustrated by differ from the devices 12 in providedwith the plane of the strings as shown.

Tie arrangement shown has the further advantage of eliminating theintroduction of even harmonics by the translating device Into theoscillations thereby generated. With certain translating devices motionof the string in one direction, corresponding for example with apositive electric oscillathat they are tion peak, may produce adifferent change in reluctance and hence in oscillation peak pole pieces7 which may be in devices 13 in Figure 2, which i amplitude from thechange and amplitude respectively produced by similar string motion inthe opposite direction, corresponding in the same example to a negativeoscillation peak. Thus the wave-form of the oscillations is renderedasymmetrical about the axis; and such asymmetry denotes, of course, thepresence of even harmonics; which, since similar string motions in thetwo directions were assumed in the example, were not present in thestring vibration. In Figure 2 the only distinction between motion of thestring in the two horizontal directions is a difference in phase or signof the oscillation peak thereby produced, the waveform and amplitudes oneach side of the mean position being symmetrical, owing to thesymmetrical placement about the string of the two devices active intranslating its vibration into electric oscillations.

Such benefits of spurious even harmonic elimination may be obtained inthe case of strings and translating devices not specially arranged forelimination or reduction of rap. Thus in Figure 3 I show a string 1;hammer 2 arranged to excite it principally into vertical vibration, anddevices 14 arranged for most efiicient translation of such verticalstring vibration. The devices 14 may consist of two bar magnets 24, onebelow and one above string 1, with similar poles of each adjacent thestring. Thepoles are uniforml v designated N by way of example. Coils34, shown schematically, may surround magnets 24, a proper method suchthat the coils tend mechanically to form one continuous, similarlydirected winding. Translating devices 15 are of an alternative form,wherein the phase of the upper coil 35 and the polarity of the uppermagnet 25 have each been reversed. In the case of devices 15, magnets 25may be replaced with pole pieces, and a single horse shoe magnetemployed with one of its poles touching the top of the upper pole pieceand the other the bottom of the lower pole piece.

It frequently happens that the vibration of strings, particularly ofthose notcontinuously excited, does not consist of,.0r may not beresolved into, relatively steady components at right angles to eachother, such as horizontal and vertical components; but instead may beresolved into continuously varying such components, of which the vectorsum is probably relatively steady. Thus the apparent plane of vibrationmay shift continuously, either as a continuous rotation of such planeabout the mean position of the string as an axis or as a pendularoscillation of such plane back and forth about such axis. lVith mostforms of translating device this action causes amplitude of the electricoscillations produced, which may prove objectionable. have found itdesirable for the reduction or of connection being.

a continuous change in the.

elimination of this effect to curve or dish the pole of the magnet (orole piece if employed) generally, thong not necessarily exactly,following a section of a cylinder having the string as its axis. Thus inFigure 4 I show in cross-section string 1 and the translating devices 14of Figure 3, the section being along line 4-4 of Figure 3. The ends ofthe magnets 24 of the translating devices 14 adjacent string 1 are seento be dished or curved as described. It will be appreciated that theplane of vibration of the string may shift materially from the verticalwithout appreciable changing the relationship of the string at any giveninstant to the curved pole surfaces of the magnets 24. This curving ofthe pole surface may equally advantageously be employed with a singletranslating device such as either the lower or upper translating device14.

Further details of my invention appear in Figure'fi. In this figure 1and 1 are sections of strings, excitable by hammers 2 and 2'. Underneathstrings 1 and 1 are shown respectively translating devices 16 and 16,which may comprise magnets 26 and 26 and coils 36 and 36, the latterbeing preferably connected in series. \Vhile 1-2 and 1-2' are shownrespectively in different horizontal planes, 26 and 26' different inlength, and

16 and 16' in different longitudinal positions,

it will be understood that those differences need not exist, beingincorporated in the figure for the sake of clear depiction. Thetranslating devices 16 and 16' may be mounted in block 51, which iscarried by base 56.

Base 56, although illustrated in its normal position, will also be seento be hinged to string support 57 by hing-e 58. This permits itsmovement away from the strings, as to the position shown in dottedlines; and handle 59 may be provided to facilitate such motion. Whenbase 56 is so moved, block 51 and the translating devices are lowered inposition away from the strings, resulting in uniformly decreasedtranslation cfiiciency. Thus a general control of oscillation amplitude,or of output volume from loudspeaker 5, is provided by movement of thetranslating devices.

In Figure 5 I also show means for adjusting the amplitudes of theoscillations produced by the individual translating devices with base 56in any given position and with any given amplitude of string vibration.The magnets 26 and 26 of the translating devices 16 and 16' are seen tobe inserted in holes 61 and 61"in block 51; and they may be raised orlowered in such holes to any desired position and there secured by meansof i set screws 62 and 62. Thus not only may inequalities in theamplitude of the oscillations produed by a given amplitude of vibra- Ition of the several strings be eliminated, but

compensation may be effected for inequalities in actuation mechanismsfor the several strings and in the amplification efficiency of amplifier2 and translation efiiciency of loudspeaker 5 at different frequencies;furthermore special and unusual frequency-loudness characteristics maybe thus imparted to the complete instrument if desired.

In'Figure 6 I show a gered arrangement of translating devices. Here thestrings I may be strung in a plane, as between the sides of a frame 70,and hammers 2 below the strings may be provided to excite the same.

To the frame 70, as to the bottom thereof, may be secured block 72,carrying a plurality of translating devices 17. These may each consistof a vertical bar magnet 27 carrying nearits upper pole coil 37; andeach magnet may be adjustably held in place in a hole in block 72 by aset screw 63. The magnets are preferably of wide, thin stock, and thecoils are arranged in two rows, those in each row being staggered withres eet to those in the other. The coils are pre erably electricallyconnected in series so that all the translating devices producesimilarly directed voltages in the common circuit for a given directionof motion of the strings, either upward or downward.

In Figure 6 I also show a preferred meth- 0d of connection to anelectrical amplifier 4 translating of a group of translating devicesassociated with different frequency strings. Of the input terminals ofsuch an amplifier one is frequently effectively connected to groundeither directly or through a low reactance or impedance, while the otheris of relatively free potential. A typical illustration is an amplifyingtube input, which is illustrated for example in dotted lines in the boxof amplifier 4 in the figure, wherein one input terminal connects almostdirectly to the cathode system with its usual low or ground potentialand the other to the grid of the tube, separated from any low potentialby at least a very high value of resistance. It is highly desirable toconnect to the free-potential input terminali. e., the grid of the tubein amplifier l-that extremity of the group of devices which isassociated with the highest frequency strings; otherwise the efficiencyof the instrument at such frequencies and their natural harmonics may beseriously impaired.

While in describing the foregoing embodiments of my invention I haveshown electromagnetic translating devices, my invention is not peculiarthereto and I do not wish so to limit it, these embodiments beingequally applicable to and useful with other forms of translating device,as will be understood.

In Figure 7 I show an alternative form of translating device in which nocoils need be employed. With this form strings I may be used, strungfrom one tuning pin to the plan view of a stagnext, for example in ahorizontal plane, over individual pressure bars 84 and around pins 81,respectlvely on and in insulatin tops 83of a frame 70. In a that laneunderneat of the strings and in a line cutting across the strings may beplaced bar 87 of magnetic material such as soft iron. Vertical bar manets 86 mag be fastened to bar 82, alternatefy poled; an to the toppoles of the magnets 86 may be fastened pole pieces 85, lying in theplane of the strings. A cross sectional view of the assembly of Fi ure7, taken along the line 88, appears as igure 8. In this figure theletters N and S, alternately appearing by the lower poles of the magnets86,

denote their alternate polarity. The several strings are caused to formone continuous series circuit-by the connections 87 appear ing in Figure7 and this circuit may be connected to the input terminals of anelectrical amplifier 4, preferably including a step-up transformer 88.Loudspeaker 5, as in vious figures, is shown connected to theoutputterminals of amplifier 4.

Each of the strings will be seen to ass through a gap between two of thepole pieces 85. Each of these gaps contains a high flux, each gap beingpart of a magnetic circuit comprising the adjacent ole pieces, themagnets touching these poles, and the section of bar 82 between thesemagnets. Each string 1, being caused by its hammer 2 to vibrate with alarge vertical component, cuts the magnetic lines in its gap and thusthere is induced in the string an a. c. voltage of frequencycorresponding to that of the string vibration. 'The a. c. voltageappearing in the string circuit as a result of the vibration .of manystrings as may be simultaneously vibrat ng 1s stepped up by transformer88, amplified by amplifier 4 andtranslated into sound by loudspeaker 5.Various modifications of the arrangement illustrated in Figures 7 and 8may of course be effected without departing from the spirit of theinvention, which is intended to embrace the translation of the vibrationof a tuned string into electric oscillations in the stung by suitableplacement of the latter in a steady magnetic field.

It will be seen that all the devices hereinabove disclosed-are withoutmoving or vibratmg parts, and operate without mechanical connection tothe vibrating body: they may therefore be classed as operativelystationary. In Figure 9, however, I show a translatmg device intended tofunction at the end of the active portion of a string or of each stringin a group, and having an operating mechanical connection to thestrings. As in prior figures, the strings and the hammers herein arerespectively designated as 1 and 2. The strings are each passed over anedge 89 of electrically conductive block 90 and may be secured to pins91 in electrically conducpretive block 92. The latter are so positionedas to cause the strings by'virtue of their tension to bear down upon theedge 89 of block 90; and this downward pressure is transmitted .to block96, of piezo-electrio material such as quartz- Block 96 is thus placedin compression between block 90 and electrically conductive plate 93,which may be mounted to and insulated 'from the base 95 b insulatingblock 94. The strings 1 are el ectrically connected together and toblock 92; and this may be connected to one input terminal, preferablythe ground or low tential terminal, of electrical amplifier 4, to theother input terminal of which may be connected the plate 93.

This translating device makes use of the property of the generation ofvoltagejn, by varlation of pressure on, piezo-electnc material, thelatter being in general substituted for the bridge of the usual purelymechanical and acoustical musical instrument, as will be understood. Inan instrument containing a lar e number of strings a singlepiezo-electric lock for all strings, for each group of strings, or foreach string, may be employed as desired.

It will be understood that while I have shown and described theembodiments of my invention in connection with strings, they may readilybe employed with other forms of vibrators; and that variousmodifications may of course be made in the choice and disposition ofcomponent parts without departing from the spirit or scope of myinvention, as hereinabove disclosed and in the appended claims defined.

I claim 1. In a musical instrument, the combination of a tuned vibratorand means for producin therefrom electric oscillations of smooth initialam litude rise, said means comprising means or roducinga deflection ofsaid vibrator, where y the same is set into vibration, andmechanico-electric translating means sensitive to said vibration andrelatively insensitive to said initial deflection.

2. In a musical; instrument, the combination of a tuned vibrator andmeans for producing a sound of smooth inception therefrom, said meanscomprising means for exciting said vibrator to initiate vibrationthereof, mechanico-electric translating means energized by saidvibrator, said translating means being relatively insensitive to motionsof said vibrator immediately attendant upon said excitation, andelectro-acoustic translating apparatus connected to saidmechanicoelectric translating means.

3. In a musical instrument, the combination of a tuned vibrator andmeans for producing therefrom electric, oscillations of smooth initialamplitude rise, said means comprising percussive means active in a givenplane for exciting said vibrator into vi-- mechanico-electrictranslating means relatively unres onsive to components of saidvibration in sai given plane and relatively responsive to components inother planes.

v 4. In a musicalinstrument, tion of a tuned string and means forroducing therefrom electric oscillations re atively free of initialtransients, said means comprismg a hammer adapted to strike said stringand mechanico-electric translating means enargued by said string, saidtranslating means being relatively insensitive to motions of said stringimmediately attendant upon such striking.

5. In a musical instrument, the combination of a string; a hammeradapted to strike sa1d string; and a mechanico-electric translatingdevice having a (portion in spaced relatlon to said string an operativein accordance with vibratory variation of the spacin between said stringand the surface of sai port1on, said portion being arranged without theplane in which said hammer moves when striking said string.

6. In a musical instrument, the combination of a string; a hammeradapted to strike said strin and a mechanico-electrio translating devicehaving a ortion in spaced relation to said string and operative inaccordance with vibratory variation of the spacin between said stringand the surface of sai portion, said portion being arranged withoutbration, and

the combinatheplane in which said hammer moves whenstriking said string,and said surface being substantially parallel to said plane.

7. In a muslcal instrument, the combination of a succession oftunedvibratory bodies ly- 1ng substantlally in a plane;amechanicoelectric translating system having portions respectivelypositioned between each two succeedin bodies and being arranged totranslate into electric oscillations components of vibration of saidbodies in said plane; and a striker for each of said bodies movable in aplane substantially different from said first mentioned plane.

8. In a musical instrument, the combination of a tuned string; means forvibrating sa1d string; a mechanico-electric translating device having aportion in spaced relation to a section of said string and arranged tobe actuated by vibratory variation of such spacmg; and a curved surfaceon said portion, said surface tending to follow a section of a cylinderabout the mean position of said strin as an axis.

9. n a musical instrument, the combination of a string; means forvibrating said string; and a mechanico-electric translating device havina portion arranged adjacent and symmetrically to said string andoperative in accordance with vibratory variation of such spacing, themid part of said portion being recessed.

10. In a musical instrument, the combination of a plurality of tunedbodies; means for vibrating. said bodies; mechanico-electric translatingapparatus having. a portion adjacent each of said bodies and beingarranged to be actuated by vlbratory changes in the distances betweensaid bodies and said portions; and a single means connected to all ofsaid portions for simultaneously and similarly adjusting the distancesbetween said bodies and said portions.

11. A musical instrument comprislng a plurality of tuned bodies; meansfor vibrat-- ing each of said bodies at a plurality of its partialfrequencies; mechanico electric translating apparatus for translatingthe vibrations of said bodies into electric oscillations, said apparatushaving portions respectively adjacent said bodies and being arranged tobe actuated by vibratory variation of the spacings between said bodiesand said portions; electro-acoustic translating apparatus fortranslating said oscillations into sound; and means individuallyconnected to the second said portions of said mechanico-electrictranslating apparatus for adjustably securing said portions, whereby theseveral said spacings may be individually ad usted.

12. The method of varying the output volume of a musical instrument ofthe type wherein the vibrations of tuned bodies are translated intoelectric oscillations by vibratory variation of the distances betweensaid bodies and stationary translating apparatus, which consists insimultaneously and similarly varying the distances between said bodiesand said apparatus.

13. The method of voicing a musical instrument of the type wherein thevarious partial frequency vibrations of each of a plurality tuned bodiesare translated into sound by a mechanico-electro-acoustic translationprocess including the vibratory variation of the distances between saidbodies and stationary translating apparatus, which method consists inselectively adjusting the distances betwen said bodies and saidapparatus.

14. In a musical instrument, the combination of a tuned vibrator, twosubstantially similar operatively stationary mechanicoelectrictranslating devices in substantially similar spaced relation torespectively opposite sides of a portion of said vibrator, andelectrical connections between said translating devices wherebyoscillations of the fundamental vibrational frequency of said vibratorrespectively translated by said devices mutually aid.

15. In a musical instrument, the combination of a tuned vibratory body;means for maintaining a magnetic field transversely through a portion ofsaid body between its extremities; means for vibrating said body in aplane substantially normal to said field; an electrical work circuithaving two input terminals; and electrical connections between said twoextremities of said body and said input terminals. I

16. In a musical instrument, the combination of a plurality of tunedstrings electrically connected in series to form a single circuit; meansfor maintaining a magnetic field transversely through each of saidstrings; means for vibrating each of said strings in a planesubstantially normal to said field; an electrical work circuit havingtwo input terminals; and electrical connections between the extremitiesof said string circuit and said input terminals.

17. In a musical instrument, the combinat on of a block ofpiezo-electric material; an electrically conductive member in contactwith one face of said block; at least one tuned string exerting pressureupon a portion of said block opposite said face; means for vibratingsaid strings, whereby their pressure upon said block is oscillatorilyvaried; and means for translating into sound electric oscillationsthereby generated in said block.

18. In a musical instrument, the combination of a plurality ofprogressively tuned ;vibratory bodies; means for vibrating said bodies;an electrical series of translating devices associated with saidvibratory bodies, a first extremity of said series being associated withat least one of said bodies tuned to a low frequency and the secondextremity with at least one of said bodies tuned to a high frequency; anelectrical amplifier having an input terminal separated from ground bynot more than a relatively low impedance and a second input terminalseparated from ground by at least a relatively high impedance; and aconnection from said first extremity of said series to said firstamplifier input terminal and a connection from said second extremity tosaid second amplifier terminal.

BENJAMIN F. MIESSN ER.

